1Program in Physical Therapy, Washington University School of Medicine, 2Program in Occupational Therapy, Washington University School of Medicine, 3Department of Neurology, Washington University School of Medicine, 4Mallinckrodt Institute of Radiology, Washington University School of Medicine, 5Department of Biomedical Engineering, Washington University

1Center for Visual and Neurocognitive Rehabilitation, Atlanta VAMC, Department of Medicine, Division of General Medicine and Geriatrics, Emory University School of Medicine, 2Harvard Neurology Residency Program, Brigham and Woman‘s Hospital and Massachusetts General Hospital

People are social chameleons and regularly engage in nonconscious behavioral mimicry. This occurs when an individual unwittingly imitates the behaviors of another person, such as crossing one's legs moments after a person sitting adjacent does so, or adjusting one's body posture to match a conversation partner. Rapport between two people increases behavioral mimicry, just as mimicry also increases rapport. Psychologists have posited that this mimicry is attributed to a perception-behavior link;1 seeing a person engage in a behavior activates that behavioral representation, which then makes the perceiver more likely to engage in that behavior him- or herself.
The following experiment expands on these previous findings by testing whether people, without intention or awareness, use mimicry to their advantage. Because goals activate behavioral strategies and plans of action that help people pursue those goals,2 Lakin and Chartrand hypothesized that individuals would mimic another person more when they have a goal to affiliate than when they do not.3…

1Motion Analysis Laboratory, Kennedy Krieger Institute, 2Physical Medicine & Rehabilitation, Johns Hopkins University School of Medicine, 3Johns Hopkins University School of Medicine, 4Department of Neurology, Johns Hopkins University School of Medicine

A factorial design is a common type of experiment where there are two or more independent variables. This video demonstrates a 2 x 2 factorial design used to explore how self-awareness and self-esteem may influence the ability to decipher nonverbal signals. This video leads students through the basics of a factorial design including, the nature of a factorial design and what distinguishes it from other designs, the benefits of factorial design, the importance and nature of interactions, main effect and interaction hypotheses, and how to conduct a factorial experiment.…

We generally think that we see things pretty well if they are close by and right in front of us. But do we? We know that visual attention is a property of the human brain that controls what parts of the visual world we process, and how effectively. Limited attention means that we can't process everything at once, it turns out, even things that might be right in front of us.
In the 1960s, the renowned cognitive psychologist Ulrich Neisser began to demonstrate experimentally that people can be blind to objects that are right in front of them, literally, if attention is otherwise distracted. In the 1980s and 1990s, Arien Mack and Irvin Rock followed up on Neisser's work, developing a simple paradigm for examining how, when, and why distracted attention can make people fail to see the whole object. Their experiments, and Neisser's, did not involve people with brain damage, disease, or anything of the sort, just regular people who failed to see objects that were right in front of them. This phenomenon has been called inattentional blindness. This video will demonstrate basic procedures for investigating inattentional blindness using the methods of Mack and Rock.1…

1Discipline of Exercise and Sport Science, Faculty of Health Sciences, University of Sydney, 2Department of Sport, Health and Exercise Science, University of Hull, 3Academic Vascular Department, Hull Royal Infirmary, Hull and East Yorkshire Hospitals, 4Department of Vascular Surgery, Addenbrookes Hospital

In 1959 The 3 R's were introduced by W.M.S. Russell and R.L. Burch in their book The Principles of Humane Experimental Technique. The 3 R's are replacement, reduction, and refinement of the use of animals in research.1 The use of cell lines and tissue cultures that originated from research animals is a replacement technique, as it allows for many experiments to be conducted in vitro. Harvesting tissues and organs for use in cell and tissue cultures requires aseptic technique to avoid contamination of the tissues. Sterile harvest is also necessary for protein and RNA analysis and metabolic profiling of tissues. This manuscript will discuss the process of sterile organ harvest in rats and mice.…

Equilibrium is a special case in mechanics that is very important in everyday life. It occurs when the net force and the net torque on an object or system are both zero. This means that both the linear and angular accelerations are zero. Thus, the object is at rest, or its center of mass is moving at a constant velocity. However, this does not mean that no forces are acting on the objects within the system. In fact, there are very few scenarios on Earth in which no forces are acting upon any given object. If a person walks across a bridge, they exert a downward force on the bridge proportional to their mass, and the bridge exerts an equal and opposite upward force on the person. In some cases, the bridge may flex in response to the downward force of the person, and in extreme cases, when the forces are great enough, the bridge may become seriously deformed or may even fracture. The study of this flexing of objects in equilibrium is called elasticity and becomes extremely important when engineers are designing buildings and structures that we use every day.…

The collection of blood from mice and rats for analysis can be done through a variety of methods. Each method of collection has variations in the type of restraint required, the invasiveness of the procedure, and the necessity of a general anesthetic.1Historically, the use of the retro-orbital sinus cavity has been used, but not without debate. The controversy related to the potential tissue damage,or even blindness,caused by retro-orbital bleeds has led to the development of facial and submandibular vein bleeding methods in mice.Blood collection from the saphenous vein in both mice and rats is another technique that has been developed. These procedures do not require anesthesia and therefore are suitable when the use of anesthetics may confound blood results or other data.
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1Department of Molecular and Experimental Medicine, Dorris Neuroscience Center, The Scripps Research Institute, 2Department of Cellular and Molecular Medicine, University of California San Diego, 3Department of Bioengineering, University of California San Diego, 4Department of Neurosciences, University of California San Diego School of Medicine

Human memory is limited. Throughout most of its history, experimental psychology has focused on investigating the discrete, quantitative limits of memory—how many individual pieces of information a person can remember. Recently, experimental psychologists have also become interested in more qualitative limits—how precisely is information stored?
The concept of memory precision can be both intuitive and elusive at once. It is intuitive, for example, to think a person can remember precisely how their mother sounds, making it possible to recognize one’s mother immediately over the phone or in a crowd. But how can one quantify the precision of such a memory? Exactly how similar is the memory to the voice itself?
To study the precision of memory and working memory, in particular, experimental psychologists have devised a paradigm known as delayed estimation. It has been used most often, thus far, to study the precision of visual memories, especially memory for color, and to understand how memory degrades the more one tries to remember at once. This video demonstrates standard procedures for investigating the precision of color working memory using delayed estim…

Human memory seems to work in two broad ways. Like modern computers, the human mind has explicit, or declarative, memory: ask a question, and a person gives the best answer they can. Input a query, and a computer program returns the contents of the relevant parts of its stored memory.
Humans also have a second kind of memory system, one not really typical of computers, one that experimental psychologists call implicit.
Implicit memory is a broad term that refers to the many ways past experiences influence present behavior. Pavlov’s famous dogs, for example, learned to associate the sound of a bell with mealtime. Eventually, they began salivating whenever they heard a bell, even if food was not delivered.
Humans also possess implicit memory. Implicit memories, for example, are the reason it can be difficult to fall asleep in a new place; people associate their bedroom environment and their nighttime routines with sleepiness.
Implicit memory is thought to guide human behavior in a wide array of circumstances. It is the kind of memory that guides manners and social behaviors, the kind of memory that puts relevan…

It is obvious that we are influenced by those around us, but in the early to mid 1900's, psychologists began to study how potent social influence can be on our thoughts and behaviors. Motivated in part by attempts to explain the behaviors of Nazi soldiers in World War II, one topic of considerable interest at the time in psychology was conformity, the phenomenon in which people match their attitudes, behaviors, or beliefs to group norms.
While behaviorist psychology explained conformity in terms of simple reinforcement learning (e.g., it is rewarding to follow the group), Gestalt psychologists argued that conformity is the result of perception being determined just as much by our social world as the physical world. Starting in 1951, Solomon Asch conducted a series of experiments to test the Gestalt idea that group norms can influence our perception of the world, even when the group norm is incorrect in a judgment of something that can be measured objectively. The experiments involved participants making a judgment about which of three comparison lines matched the length of a standard line. The experiments consisted of a group of people who were confederates with the exception of the one participant, and on certain judg…

Imagine the sound of a bell ringing. What is happening in the brain when we conjure up a sound like this in the "mind's ear?" There is growing evidence that the brain uses the same mechanisms for imagination that it uses for perception.1 For example, when imagining visual images, the visual cortex becomes activated, and when imagining sounds, the auditory cortex is engaged. However, to what extent are these activations of sensory cortices specific to the content of our imaginations?
One technique that can help to answer this question is multivoxel pattern analysis (MPVA), in which functional brain images are analyzed using machine-learning techniques.2-3 In an MPVA experiment, we train a machine-learning algorithm to distinguish among the various patterns of activity evoked by different stimuli. For example, we might ask if imagining the sound of a bell produces different patterns of activity in auditory cortex compared with imagining the sound of a chainsaw, or the sound of a violin. If our classifier learns to tell apart the brain activity patterns produced by these three stimuli, then we can conclude that the auditory cortex is activated in a distinct …

Psychophysics is the name for a set of methods in perceptual psychology designed in order to relate the actual intensity of stimuli to their perceptual intensity. One important aspect of psychophysics involves the measurement of perceptual thresholds: How bright does a light need to be for a person to be able to detect it? How little pressure applied to the skin is detectable? How soft can a sound be and still be heard? Put another way, what are the smallest amounts of stimulation that humans can sense? The staircase procedure is an efficient technique for identifying a person's perceptual threshold.
This video will demonstrate standard methods for applying the staircase procedure in order to identify a person's auditory threshold, that is, the minimal volume necessary for a tone to be perceived.…

Why do people have two forward-facing eyes? By presenting the brain with two ever so slightly different images it becomes possible to comprehend visual problems that are far more difficult to process through a single eye. Chief among these is the problem of 3-D perception, seeing the world in three dimensions, despite retinal inputs in only two dimensions.
What happens if each eye receives two completely different images? That does not happen in nature, to be sure, but it can be contrived in the laboratory in a set-up called binocular rivalry.
Binocular rivalry is a common laboratory paradigm for investigating the ways that the brain integrates information from two eyes, and in recent years, the mechanisms responsible for producing conscious experience.…

Social psychologists have long been interested in the way people form impressions of others. Much of this work has focused on the errors people make in judging others, such as the exaggerated influence of central traits (such as "warm" and "cold"), the insufficient weight given to the context in which others' behavior takes place, and the tendency for people to make judgments that conform to their initial expectations about another. However, this focus on errors masks the fact that people are quite good at making fairly accurate judgments about other people's characteristics, an ability that was no doubt important over the course of human evolution.
Indeed, the human ability to make quick sense of social situations and people ranks among our most valuable skills. What is particularly impressive about our ability to make sense of others is not just how little information we need to make inferences, but how well calibrated we can be with so little information. This video shows some experimental techniques used by psychology researchers, including Ambady and Rosenthal in their seminal work,1 and explores the process of making inferences in the context of students' evaluati…

1Department of Urology, University of Minnesota, 2Masonic Cancer Center, University of Minnesota, 3Microbiology, Immunology, and Cancer Biology Graduate Program, University of Minnesota, 4Department of Medical Microbiology, Immunology and Cell Biology, Southern Illinois University School of Medicine, 5Simmons Cancer Institute

1Molecular and Cellular Biology Program, University of Massachusetts, Amherst, 2Neuroscience and Behavior Program, University of Massachusetts, Amherst, 3Department of Biochemistry and Molecular Biology, University of Massachusetts, Amherst

Classical economic theory asserts that people are rational and self-interested. In addition to seeking wealth and status, people are motivated by other goals. As a result, financial motives can sometimes be dwarfed by other internal needs, such as maintaining a positive self-concept or affiliating with other group members.
Ethical dilemmas, such as the temptation to cheat on taxes, can result when these motives are in conflict. On the one hand, people may be tempted to save money by underreporting their taxable income. On the other hand, no one wants to perceive themselves as a dishonest, free-rider. As a result, people are reluctant to fully exploit unethical opportunities because doing so can severely undermine their self-image as morally upstanding individuals. Instead, people cheat to a much smaller degree than they are capable of: just enough to gain additional resources, but not so much as to compromise their self-image.
This tendency for marginal dishonesty, or the "fudge factor," is an important principle in social psychology and can be tested through a variety of techniques. Mazar, Amir, and Ariely originally described six separate experiments involving (dis)honesty and a theory of se…